Technologically, a lot has been done under the hood since 1995 just to allow modern hardware to work. USB devices, wireless NICs, and multicore CPUs didn't even exist when Windows95 was released. Much of the "innovation" is unseen.

While I also wish they had innovated the UI more over the past decade, we are probably in the (admittedly growing) minority. You shouldn't switch the gas and break pedals in a car just to be "innovative", and I think for Microsoft the risk of alienating old users outweighs the risk of losing new users.

Apple of course has been more free to make sweeping changes to their OS over the past decade because, frankly, they haven't had much to lose. It will be interesting to see how dramatically they change OSX now that they have found something that sells.